The myocardium and pericardium are both part of the heart wall, but they have distinct structures and functions.
Myocardium vs. Pericardium: Key Differences
| Feature | Myocardium | Pericardium |
|---|---|---|
| Definition | The middle and thickest layer of the heart wall. | The outer layers of the heart wall, enclosing the heart. |
| Composition | Primarily cardiac muscle tissue. | A sac-like structure composed of two layers (fibrous and serous). |
| Function | Responsible for the heart's pumping action through muscle contractions. | Protects the heart, anchors it within the mediastinum, and prevents overfilling. |
| Location | Located between the epicardium (outer layer) and endocardium (inner layer). | Forms the outermost covering of the heart. |
Myocardium Explained
The myocardium is the heart muscle itself. As the reference states, "(Myo- means 'muscle.') Most of the heart wall is the myocardium." This layer is crucial for the heart's ability to contract and pump blood throughout the body. It also contains the heart's electrical conduction system.
- Contains the cardiac electroconductive system:
- SA node
- AV node
- HIS fibers
- Purkinje fibers
Pericardium Explained
The pericardium is a double-layered sac that surrounds the heart. The reference says that it "makes up the outer layers of the heart wall, enclosing the heart." It provides protection and support, and helps to prevent the heart from overfilling with blood.
- Layers of the Pericardium:
- Fibrous Pericardium: The tough, outer layer that anchors the heart.
- Serous Pericardium: A thinner, inner layer with two parts:
- Parietal layer: Fused to the fibrous pericardium.
- Visceral layer (Epicardium): Adheres directly to the heart surface.
